An abandoned home sits on the edge of the Jordanian-Syrian border in Sahel Houran. (Taylor Luck/For The Washington Post)

— Mohammed Hamad and his cousins, many handling a firearm for the first time, awkwardly balanced Kalashnikov rifles on their shoulders and shot practice rounds at watermelon targets here at the edge of the Yarmouk Valley separating Jordan and Syria.

“We want those Syrian dogs to hear our message,” the teacher, 35, said to his informal six-man militia. “If they come, we are ready.”

Hamad’s brigade is one of dozens of hastily formed “citizen militias” in northern Jordan, the self-appointed guardians of communities living at the edge of a war next door in Syria that is inching toward the border. For weeks, the ragtag forces have spent evenings patrolling the mountainous frontier region and monitoring what Jordanian officials and Syrian opposition activists say is a Syrian military escalation in the south. Residents here fear it may be a prelude to an invasion.

Despite the apparent movement of Syrian tanks and troops toward the border, tensions between the official militaries of Jordan and its northern neighbor have been limited to occasional exchanges of gunfire and warning shots from Syria when errant mortar shells sail toward Jordanian patrol units.

Yet, as Damascus ratchets up a month-long military offensive that has led to the capture of key rebel strongholds in southern Syria, nervous residents of northern Jordan say near-daily rocket fire and gunfire from across the border are torching farmlands, damaging houses and forcing dozens of families to flee to safer ground.

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Residents in Jordan’s border communities said that as many as four Jordanians have been killed by the firings, although the figure is disputed by Jordanian officials, who say there have been no deaths. But the scorched olive orchards and collapsed mud-brick farmhouses have spurred many people — some here say hundreds — to seek shelter with relatives or to rent apartments in towns and villages out of the rockets’ reach.

Nowhere has the impact of the border fighting been felt more than in the village of Sama Sarhan, a dusty cluster of bare concrete dwellings a few hundred yards from the Nasib border crossing, Syria’s main conduit into Jordan and the object of an intense three-month battle between government and rebel forces.

During one week last month, residents here said, as many as 50 rockets landed in and around the village. Now they enforce a strict curfew at night, and many have withdrawn their children from the local school.

Villagers have also imposed nightly electricity blackouts to prevent Syrian rebel forces from mistaking their houses for Syrian military barracks and customs offices, which lie just a few miles away.

“As soon as the lights are on, the explosions get closer,” said retired government clerk Mohammed Sarhan, 50, as he leaned back in his plastic lawn chair and watched as rocket fire from the nearby Syrian town of Nasib lit the sky above his darkened home on a recent night. “After sunset, you won’t find a single television on in the entire town.”

Several residents said that they think the rocket fire and gunshots are provocation by the Syrian military and that they are waiting for the Jordanian army to respond in kind. But Jordan, which has strived to maintain a neutral stance toward the conflict next door even as King Abdullah II calls on Syrian President Bashar al-Assad to step down, has stopped short of accusing Syria of targeting Jordanian soil.

Yet, a recent increase of Jordanian troops in the north and Prime Minister Abdullah Ensour’s admission last week that Jordan has asked the United States for Patriot missiles to station along its border have been viewed here as signs that Amman considers the incidents a national security threat.

While acknowledging that Syrian missiles are reaching deeper into Jordanian territory, military officials here play down the threat facing residents of border towns and villages.

“Jordanian citizens are not under any threat by the clashes occurring along the border,” said Brig. Gen. Hussein Zayoud, head of the Jordanian border guard.

“But that does not stop some from getting carried away” by their fears, he said.

In any case, the prospect of missile defenses has done little to calm the nerves of rattled border residents.

“A regime entering its dying days is likely to lash out at anyone and everyone around it, and Jordan is on top of the list,” said convenience store owner Mohammed Saad, 42. “We have the power and the means to strike the Assad regime, and we must use it before they strike first.”

In the village of Sahel Houran, a few miles from the battlegrounds at the base of the disputed Golan Heights, the streets remained empty save for scattered groups of soccer-playing children who darted between recently abandoned stone houses at the edge of the Yarmouk Valley.

Here, daily talk is dominated by fears about the Syrian government’s possible use of chemical weapons against rebels and communities near the border and about the involvement of the Lebanese militia Hezbollah in the Syrian conflict. Residents religiously track news reports of the battles being waged a few miles away.

“Every time we hear a rocket, we expect it to be the rocket that finally hits us,” said Abu Saleh al-Rabieh, a volunteer imam at the al-Rahman mosque, where several kneeling men recited the Koran after noon prayers as rocket fire shook the building. The mosque has doubled in recent weeks as a bomb shelter for residents, who view it as the sole sound structure in the town of 15,000.

“There is no house safer than the house of God,” Abu Rabieh Hamad, 52, said as he stood in the mosque’s entrance watching plumes of black smoke rise along the horizon.